Head tube angle maths?

sonny73 Posts: 2,203
edited April 2011 in Workshop
What is the actual height difference in mm at the bars end of the stem, between a bike frame with a head tube angle of 73 degrees and one of 73.5, if both bikes have the same head tube length and I am using the same set up and amount of spacers with a 110mm stem on both?
Thank you very much if you can answer this.


  • Berk Bonebonce
    Berk Bonebonce Posts: 1,245
    I think the bars would be a little higher and a little further away from the rider with the steeper head angle. I think we are talking millimetres, and wouldn't have thought more than 10.
  • Mister W
    Mister W Posts: 791
    The difference will depend on the height of the stack of spacers. The more spacers you have, the greater the difference, but it's likely to be a couple of mm at most (I think the reach will be less than 1mm different with a 100mm stack. That's the horizontal difference. There will be a small vertical difference as well)
  • sonny73
    sonny73 Posts: 2,203
    OK great, thanks for that. I can tell you I will be running a 15m top cap and 35mm of spacers. If that affects the difference?
  • maddog 2
    maddog 2 Posts: 8,114
    this doesn't quite tell you the answer


    but a bit of bodging suggest that the 73.5 will be 1mm longer and 1mm lower
    Facts are meaningless, you can use facts to prove anything that's remotely true! - Homer